28/04/2008 JAI Advisory Board Meeting
NS-FFAG development at JAI
PAMELA ( & EMMA )
Takeichiro Yokoi
28/04/2008 JAI Advisory Board Meeting
Introduction Non-Scaling Fixed Field Alternating Gradient(NS-FFAG) accelerator has advantages such as fast acceleration, large acceptance, and (for a fixed field accelerator) small beam excursion, flexibility in machine design, operation and variable energy beam extraction
CONFORM CONFORM ((CoConstruction of a NNon-scaling FFFAG for OOncology, RResearch and MMedicine) aims to develop the Non-scaling FFAG as a versatile accelerator. (Project HP: www.conform.ac.uk)
Two main projects are going on ….. (1) EMMAEMMA: Construction of electron machine (prototype for muon accelerator)
(2) PAMELAPAMELA : Design study of NS-FFAG particle therapy facility ( Proton & Carbon )
28/04/2008 JAI Advisory Board Meeting
~20mm ∆r/r<1%
Kinetic Energy(MeV)
T
OF/
turn
(ns)
|df/f|~0.1%
€
B0 = Δx × B1
B0
x
What is NS-FFAG ? Fixed field ring accelerator with “small dispersion linear lattice”
Small dispersion …① Orbit shift during acceleration is small
Small Magnet aperture, energy variable extraction
② Path length variation during acceleration is small fixed frequency rf can be employed for relativistic particle acceleration Fixed field linear lattice …
① Simple and flexible lattice configuration tunability of operating point
② Large acceptance
③ Large tune drift ( focusing power B/p ) Fast acceleration is required
10MeV
20MeV
/cell
/ cell
28/04/2008 JAI Advisory Board Meeting
EMMA: Electron Model for Many Applications
Daresbury labo.Daresbury labo.
Electron NS-FFAG as a proof of principle is to be built as 3-year project.(host lab: Daresbury lab.)
It is also a scaled-down model of muon accelerator for neutrino factory. Research items are . . .
(1) Research of beam dynamics of NS-FFAG
(2) Demonstration of NS-FFAG as a practical accelerator
(3) Demonstration of fast acceleration with fixed frequency RF
3mm(normalized)Acceptance
1.3GHzRF
10~20MeV(variable)Extraction energy
10~20MeV(variable)Injection energy
16.57mCircumference
42 (doublet Q) Number of Cell
5m5m
Muon Acceleration
28/04/2008 JAI Advisory Board Meeting
Standard Photons
Standard Protons
photonphoton protonproton
PAMELA :Particle Accelerator for MEdicaL Applications Particle therapy has advantages in cancer therapy
compared to X-ray therapy due to good dose concentration and better biological effectiveness (especially HI therapy).
As an accelerator for particle therapy, the advantages of FFAG are higher intensity compared to ordinary synchrotron, flexible machine operation compared to cyclotron, and simultaneous(multi-port) beam extraction
PAMELA aims to design particle therapy accelerator facility for proton and carbon using NS-FFAG with spot scanning Prototype of non-relativistic NS-FFAG (Many applications !! Ex. proton driver, ADS)
It also aims to design a smaller machine for biological study as a prototype.
Difficulty is resonance crossing acceleration in slow acceleration rate
3-ring scheme by E.Keil, A.Sessler, D.
Trbojevic
28/04/2008 JAI Advisory Board Meeting
The CollaborationEMMA ( PM: R.Edgecock ) Rutherford Appleton Lab Daresbury Lab. Cockcroft Ins. Manchester univ. John Adams Ins. BNL (US) FNAL (US) CERN LPNS (FR) TRIUMF (CA)
PAMELA (PM: K.Peach) Rutherford Appleton Lab Daresbury Lab. Cockcroft Ins. Manchester univ. Oxford univ. John Adams Ins. Imperial college London Brunel univ. Gray Cancer Ins. Birmingham univ. FNAL (US) LPNS (FR) TRIUMF (CA)
JAI team (alphabetical)
J.Cobb, K. Peach, S.Sheehy, T.Yokoi, H.Witte (+G. Morgan)
28/04/2008 JAI Advisory Board Meeting
“Linear Model, Nonlinear Reality”in the actual lattice of EMMA ... Magnet aperture ~ Magnet length ~ Magnet distance
Severe nonlinearity arises due to coupling and fringing field
Magnet pole
Fringing field is dominant!!
Center of pair magnet
2cm
QF
QD
Inter-magnet coupling introduces strong nonlinearity
~6cm
Tracking study with realistic 3D field is indispensable in machine
design
R&D asset from EMMA (1) : Tracking
28/04/2008 JAI Advisory Board Meeting
TOF
Baseline model
Tracking
Horizontal tune
Baseline model
Tracking
Vertical tune
Baseline model
Tracking
Tracking with 3D field in EMMA Tracking was carried out with ZGOUBI and 3D field map generated by OPERA/TOSCA
Validity of accelerator design based on linear model was examined and verified with 3D field tracking.
By T. Yokoi
28/04/2008 JAI Advisory Board Meeting
R&D asset from EMMA(2) : Injection& Extraction
Tracking
Big challenge in injection and extraction in EMMA is to cope with large variety of injection condition (Energy: 10~20MeV, h/cell: 0.15~0.4)
Horizontal tune
Multi-kicker system can
minimize the injection error
50mrad.
3mm
50mrad.
3d tracking by T. Yokoi
28/04/2008 JAI Advisory Board Meeting
PAMELA R&DPAMELA :PAMELA : particle therapy accelerator facility for proton and carbon using NS-FFAG with spot scanning
Research items are ….
(1) Lattice : Field quality, tolerance, acceleration
(2) Magnet : Engineering feasibility etc
(3) Extraction
(4) Acceleration Scheme
(5) Control & Diagnostics
(6) Treatment apparatus (ex gantry)
(7) Requirement as a treatment facility
28/04/2008 JAI Advisory Board Meeting
PAMELA R&D : Lattice At present, two different types of lattice are proposed for NS-FFAG of non-relativistic particle
(1) Linear lattice (by E.Keil et al.) Small excursion, large tune drift, short drift space, ordinary combined function magnet
(2) Non-Linear Lattice (by C. Johnston et al.) * sextupole for chromaticity correction Large excursion, small tune drift, long drift space, wedged combined function magnet
Cells Tunes for 30-400 MeV Tune-stablized FFAG
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.2 0.4 0.6 0.8 1
Momentum (GeV/c)
nux/cell-modelnuy/cell-modelnux/cell-approxnuy/cell-approx
In lattice design study, we are focusing on the understanding of dynamics of proton NS-FFAG : dynamics of slow resonance crossing acceleration, field quality, tolerance etc…
28/04/2008 JAI Advisory Board Meeting
PAMELA R&D : lattice (field quality etc)
Error Type Ax Ay
x 4.4 0
y 0.01 4.6
s 0.9 0
Φ 0.001 0.5
θ 0.58 0
ψ 0.007 1.00
6 combined 4.6 4.7
Ax xCOD[m]
1ERROR[m]By S.Sheehy
Using MAD-X, influences of field quality, tolerance etc. to the beam optics are being studied for the fixed energy orbits
0.1mm alignment error = 0.5mm distortion
In NS-FFAG, lattice tends to require thin large aperture combined function magnet level of field quality crucially gives influence to the magnet design ( and cost)
28/04/2008 JAI Advisory Board Meeting
PAMELA R&D : Lattice (Acceleration) Acceleration rate gives severe constraint for machine design.
Tracking study using ZGOUBI is being carried out : Acceleration rate, tolerance etc
d/dE vs d/dE d/dE vs d/dE Lattice and rf specifications are
to be fixed
Typical emittance blow up rate : tolerance :10m()
28/04/2008 JAI Advisory Board Meeting
PAMELA R&D: Magnet - Overview• Pamela
– Requires combined function magnets– Gradient: Up to 30 T/m– Dipole field: Up to 2.5T
• Challenges– Cannot be done using conventional iron dominated magnets– Superconducting magnets logical choice– Large bore (up to 116 mm)– Magnets are short (150-350 mm)
Ring 1 Ring 2 Ring 3 (EMMA)
F 15.45 T/m 16.98 T/m 30.57 T/m 4.56 T/m
D -13.10 T/m -16.53 T/m -30 T/m 3.71 T/m
Aperture F 55x16 mm2 116x26 mm2 105x14 mm2 (bore 72 mm)
Aperture D 29x30 mm2 72x42 mm2 68x22 mm2 (bore 106 mm)
Length F 0.17 m 0.26 m 0.35 m 0.055 m
Length D 0.18 m 0.27 m 0.36 m 0.065 m
28/04/2008 JAI Advisory Board Meeting
PAMELA R&D: Magnet
(by H.Witte)
•New idea: Double-helix concept–Two oppositely tiled solenoids create dipole field–Advantage: no ‘ends’ problem– any multipole field can be created **Fig is for dipole –Wedge shaped coils possible
•Conventional approach (shifted quad) •The magnet does not fit (thick winding :>120mm)• field quality problems dose not satisfy the requirement
Feasible magnet design was investigated for the case of linear NS-FFAG
28/04/2008 JAI Advisory Board Meeting
PAMELA R&D: Magnet (cont.d)
Bpeak: 6.68 T
•Performance–Integrated Dipole field: 0.932 Tm (0.7 Tm required)–Integrated gradient: 9.7T (8.25 T required)–Temperature margin: 1.6/1.4
Field homogeneity in beam aperture–About 80x24 mm2
Integrated field qualities–Gradient: better than 2x10-3
–Dipole: better than 10-4
(by H.Witte)
28/04/2008 JAI Advisory Board Meeting
PAMELA R&D: Extraction
QD QD QDQF QF QF
Kicker#2Kicker#1 Septum
Tune drift is not large for the energy region for treatment (~30%) For phase adjustment, easier than EMMA
∆p/p=+0.1
∆p/p=+03
∆p/p=+0.5
In EMMA, injection will not be a serious problem Fixed energy, single turn injection
∆p/p=+0.0 ∆p/p=+0.1
∆p/p=+0.2 ∆p/p=+03
∆p/p=+0.4 ∆p/p=+0.5
Septum boundary
28/04/2008 JAI Advisory Board Meeting
PAMELA R&D : Intensity modulation Key issues for spot scanning
Dose uniformity should be < ~2% To achieve the uniformity, precise intensity modulation is a must
Beam of FFAG is quantized. Good stability of injector and precise loss control are indispensable for medical applications
New approach to medical accelerator control is required in PAMELA
SOBP is formed by superposing Bragg peak
time
Inte
gra
ted cu
rrent
Synchrotron & cyclotron
Gate width controls dose
time
Inte
gra
ted cu
rrent
FFAG
Step size controls dose
“Analog IM”
“Digital IM”
28/04/2008 JAI Advisory Board Meeting
Spot scanning in PAMELA To investigate the requirement of injector, generation of SOBP in IMPT was studied using analytical model of Bragg peak
The study of beam intensity quantization tells intensity modulation of 1/100 is required to achieve the dose uniformity of 2%. (minimum pulse intensity:~106 proton/1Gy) Monitor is a crucial R&D item of PAMELA if 1kHz operation is achieved, more than 100 voxel/sec can be scanned in PAMELA for the widest SOBP case.
By G. Morgan
28/04/2008 JAI Advisory Board Meeting
Summary NS-FFAG is a novel accelerator concept and will open up new fields in accelerator science R&D of NS-FFAG is now undergoing. : CONFORM (1) EMMA (constructing an electron machine) (2) PAMELA(design study of particle therapy facility) Intensive studies for PAMELA are being carried out in JAI ex Lattice, magnet, facility design etc. Hopefully, this year is devoted to fixing the machine parameter and next year is for making the overall facility planning and proposal including test machine
28/04/2008 JAI Advisory Board Meeting
Scaling FFAG realizes stable betatron tune by non-linear field B/B0=(r/r0)k f()
Radial sector
Spiral sector
What is (Scaling) FFAG ?Acceleration rate of ordinary synchrotron is limited by the ramping speed of magnet (magnet PS :V=L·dI/dt, eddy loss: rot E+dB/dt=0)
Acceleration rate of fixed field accelerator is limited by acceleration scheme (in principle, no limitation)
~1.2m
KEK 150MeV FFAG
It requires large excursion combined function magnet p/p0=(r/r0)k+1
It can accelerate large emittance beam with high repetition rate (ex KEK PoP FFAG:1ms acceleration, 5000 mm·mrad)
KEK 150MeV FFAG100Hz extraction
* No tuning knob after construction!!
28/04/2008 JAI Advisory Board Meeting
Acceptance of NS-FFAG : why so
large? Acceptance is the region in the phase space in which beam
can survive during the whole process of an operation cycle. Acceptance is closely related to the operation process.
The magic in NS-FFAG is “LINEAR LATTICE”Focusing property has NO amplitude dependence Physical aperture limits the acceptance. (“no dynamic aperture”)
Acceleration rate is the key to ensure large acceptance
In linear lattice… ∆ B x
28/04/2008 JAI Advisory Board Meeting
Acceptance of Scaling FFAGIn Scaling FFAG, higher order fields inevitably contain
As amplitude gets larger, focusing force gets stronger non-linearly. x
x’
Large amplitude beam is lost when it hits resonance
In scaling FFAG, operation point is the keyIn scaling FFAG, operation point is the key
Large acceptance is realized through field distribution, and transverse dynamics are decoupled to longitudinal dynamics
28/04/2008 JAI Advisory Board Meeting
Resonance Crossing Acceleration Resonance is a coherent effect Fast acceleration can circumvent the problem
EMMA is a unique system to observe the transient process of resonance precisely. Unique playground for non-linear dynamics
EMMA is a unique system to observe transient process of resonance precisely. Unique playground for nonlinear dynamics !!
x
x’
Field error
10MeV
20MeV
/cell
/ cell
Fixed frequency rf is available for relativistic particle due to due to small variation of path length
Field error
Kinetic Energy(MeV)
T
OF/
turn
(ns)
|df/f|~0.1%
Fast asynchronous Fast asynchronous accelerationacceleration(In EMMA, Acceleration completes
within 10turns(~500ns))
* It is originally for muon accelerator for neutrino factory
10MeV
20MeV
28/04/2008 JAI Advisory Board Meeting
PAMELA R&D: AccelerationTwo approaches in NS-FFAG for non-relativistic beam acceleration……
(1) Harmonic number jump (A. Ruggiero)
(2) Frequency modulation
Fixed frequency RF (high Q rf : high gradient)
Amplitude modulation
low Q rf (low gradient)
no need of amplitude modulation
(adiabatic capture requires AM)
Can high Q cavity accommodate amplitude modulation ?
Can beam be accelerated sufficiently fast?
How fast beam should be accelerated in NS-FFAG ?How fast beam should be accelerated in NS-FFAG ?* Now, preparing for the study
28/04/2008 JAI Advisory Board Meeting
PAMELA R&D :Extraction
This region is common for all the extraction energy range
Varying the kicker field (max 3kgauss, 0.1kgauss step), beam position
at septum was plotted
∆p/p=+0.0 ∆p/p=+0.1
∆p/p=+0.2 ∆p/p=+03
∆p/p=+0.4 ∆p/p=+0.5
Septum boundary
28/04/2008 JAI Advisory Board Meeting
Lattice for PAMELANS-FFAG : Fixed field ring accelerator with small dispersion linear lattice
Small dispersion… Merit small magnet aperture small path length variation
Demerit many cells (small bending angle) (short straight section)
For EMMA, small dispersion linear lattice is a requirement :Demonstration machine for muon “Gutter” acceleration
For PAMELA, Optimization from the point of view of tune drift and acceleration scheme have higher priorities ( large acceptance is not required)
Linear Lattice… Merit simple structure Large acceptance
Demerit Large tune variation